The disclosed embodiments of the present invention relate to radio frequency transmission, and more particularly, to a radio frequency transmitter with an extended power range, and a related radio frequency transmission method.
As digital radio design may offer many benefits, such as reduced circuit size and prolonged battery life, it is desired to convert analog intensive designs into digitally intensive designs. For example, a radio frequency (RF) transmitter may employ a digital power amplifier (DPA) to enhance power efficiency, wherein the DPA may include a plurality of power cells controlled by an amplitude control word (ACW) signal, and an output power of the DPA may be controlled in a digital manner.
However, digital power control of the DPA limits a dynamic power range thereof. In high power application, a saturation power may limit an output power of the DPA; in low power application, quantization errors may occur. Additionally, power efficiency of the DPA is decreased due to a digital power back-off. The digital power back-off also limits the dynamic power range. Further, the saturation power of the DPA is varied in response to process variations, thus degrading performance of the DPA.
Thus, there is a need for a novel power amplifier to extend the dynamic transmission power range, enhance the power efficiency and reduce sensitivity to process variations.